In general, a microphone apparatus or the like including a microphone housing and a vibrating portion is known. Such microphone apparatus are disclosed in Japanese Laid-Open Patent Application No. 2002-191089 and Japanese Laid-Open Patent. Application No. 2007-178133, for example.
In Japanese Laid-Open Patent Application No. 2002-191089, there is disclosed a noise-canceling microphone including a sound case in the form of a tubular container, a diaphragm arranged in this sound case and an acoustoelectric conversion unit arranged in the sound case for converting vibration of the diaphragm to an electric signal. In this noise-canceling microphone, a plurality of sound input holes whose number and magnitude (shape of openings) are properly adjusted are provided on each of the front surface, the back surface and the side surface of the sound case surrounding the diaphragm. Thus, the noise-canceling microphone is formed to be capable of canceling noise (background noise) made around the sound case by making the microphone reliably acquire sounds, included in external sounds, directly reaching the diaphragm from the front surface side of the sound case while making not only the sounds from the front surface side of the sound case but also sounds input from the sound input holes on the back surface and the side surface of the sound case reach the back surface side of the diaphragm at the same sound pressure level as that on the front surface side.
In Japanese Laid-Open Patent Application No. 2007-178133, there is disclosed a semiconductor device including a pressure sensor module in which a semiconductor chip (sound pressure sensor chip) is mounted on the surface of a plate material unit having one opening on the side surface and a bathtub-shaped lid body covering the pressure sensor module from above and having one opening on the upper surface. In this semiconductor device, the plate material unit is constituted of a base substrate in which a through-hole is provided at a position where the semiconductor chip is mounted and two sheet layers provided on the back surface of the base substrate and stacked in order of a first sheet layer and a second sheet layer from the side of the substrate. The base substrate and the second sheet layer hold the first sheet layer previously provided with a slit-like notched groove from both sides, thereby forming an external communication hole communicating with the exterior at the opening on the side surface of the plate material unit from the sound sensor chip (lower surface of a diaphragm) through the through-hole of the base substrate and the inner portion of the plate material unit in the inner portion (notched groove of the first sheet layer) of the plate material unit. Thus, this semiconductor device is constituted as a differential microphone apparatus detecting the difference between a sound pressure reaching the sound sensor chip (upper surface of the diaphragm) through the opening provided on the upper surface of the lid body and a sound pressure reaching the sound sensor chip (lower surface of the diaphragm) from an opening provided on a side portion of an apparatus body through the external communication hole in the plate material unit. The semiconductor device is so formed that the openings provided on the respective ones of the upper surface of the lid body and the side surface of the plate material unit are independently arranged at positions separating from each other.